Created
July 13, 2022 07:42
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根据YouTube上写的缓存Map
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import java.util.HashMap; | |
import java.util.Map; | |
public class LRUCache<T> { | |
private final int capacity; | |
private int size; | |
private final Map<String, Node> hashMap; | |
private final DoublyLinkedList internalQueue; | |
public LRUCache(int capacity) { | |
this.capacity = capacity; | |
this.hashMap = new HashMap<>(); | |
this.internalQueue = new DoublyLinkedList(); | |
this.size = 0; | |
} | |
public T get(final String key) { | |
Node node = hashMap.get(key); | |
if (node == null) { | |
return null; | |
} | |
internalQueue.modeNodeToFront(node); | |
return hashMap.get(key).value; | |
} | |
public void put(final String key, final T value) { | |
Node currentNode = hashMap.get(key); | |
if (currentNode != null) { | |
currentNode.value = value; | |
internalQueue.modeNodeToFront(currentNode); | |
return; | |
} | |
if (size == capacity) { | |
String rearNodeKey = internalQueue.getRearKey(); | |
internalQueue.removeNodeRear(); | |
hashMap.remove(rearNodeKey); | |
size--; | |
} | |
Node node = new Node(key, value); | |
internalQueue.addNodeToFront(node); | |
hashMap.put(key, node); | |
size++; | |
} | |
private class Node { | |
String key; | |
T value; | |
Node next, prev; | |
public Node(final String key, final T value) { | |
this.key = key; | |
this.value = value; | |
this.next = null; | |
this.prev = null; | |
} | |
} | |
private class DoublyLinkedList { | |
private Node front, rear; | |
public DoublyLinkedList() { | |
front = rear = null; | |
} | |
private void addNodeToFront(final Node node) { | |
if (rear == null) { | |
front = rear = node; | |
return; | |
} | |
node.next = front; | |
front.prev = node; | |
front = node; | |
} | |
public void modeNodeToFront(final Node node) { | |
if (front == node) { | |
return; | |
} | |
if (node == rear) { | |
rear = rear.prev; | |
rear.next = null; | |
} else { | |
node.prev.next = node.next; | |
node.next.prev = node.prev; | |
} | |
node.prev = null; | |
node.next = front; | |
front.prev = node; | |
front = node; | |
} | |
private void removeNodeRear() { | |
if (rear == null) { | |
return; | |
} | |
System.out.println("Deleting key:"+rear.key); | |
if (front == rear){ | |
front = rear = null; | |
}else { | |
rear = rear.prev; | |
rear.next = null; | |
} | |
} | |
public String getRearKey() { | |
return rear.key; | |
} | |
} | |
} |
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